Recirculating incinerator

ABSTRACT

A recirculating incinerator system is disclosed wherein a burner is housed within a secondary combustion chamber for completing the combustion of the unburned products of combustion leaving the primary incinerator chamber, and for the supplying of the heat and oxygen for the burning of the refuse in the primary incinerator chamber. Within the system, a conduit containing a fan connects the incinerator chamber with the secondary chamber at a position near the burner in the secondary chamber. A second conduit is located near the opposite end of the elongated secondary chamber and it connects the secondary chamber with the incinerator chamber. A damper is located within the second conduit. Also located near the end of the secondary chamber is a stack for expelling the products of combustion to the atmosphere. By either manually or automatically controlling the fan and the damper, the circulating of hot gases containing oxygen from the secondary chamber into the incinerator chamber can be controlled in order to control the rate of burning of the refuse within the incinerator chamber.

United States Patent 1191 Potasek et al.

[111 3,716,001 1451 Feb. 13, 1973 RECIRCULATING INCINERATOR [75] Inventors: Chester J. Potasek, Fridley; Frank Hiscocks, Minneapolis, both of Minn.

[73] Assignee: Minneapolis Gas Company, Minneapolis, Minn.

22 Filed: Feb. 9, 1972 211 App]. No.: 224,674

.[ 56] References Cited UNlTED STATES PATENTS 1,995,723 3/1935 Van Denburg ..1 10/8 A 2,811,937 11/1957 Bouchard ..l lO/49 X 3,515,078 6/1970 Maitilasso.... 10/15 X 3,538,865 11/1970 Lausmann ..l10/18 Primary Examiner-Kenneth W. Sprague Att0mey.lohn D. Gould et a1.

[5 7 ABSTRACT A recirculating incinerator system is disclosed wherein a burner is housed within a secondary combustion chamber for completing the combustion of the unburned products of combustion leaving the primary incinerator chamber, and for the supplying of the heat and oxygen for the burning of the refuse in the primary incinerator chamber. Within the system, a conduit containing a fan connects the'incinerator chamber with the secondary chamber at a position near the burner in the secondary chamber. A second conduit is located near the opposite end of the elongated secondary chamber and it connects the secondary chamber with the incinerator chamber. A damper is located within the second conduit. Also located near the end of the secondary chamber is a stack for expelling the products of combustion to the atmosphere. By either manually or automatically controlling the fan and the damper, the circulating of hot gases containing oxygen from the secondary chamber into the incinerator chamber can be controlled in order to control the rate of burning of the refuse within the incinerator chamber.

7 Claims, 1 Drawing Figure RECIRCULATING INCINERATOR BACKGROUND OF THE INVENTION I. Field of the Invention This invention relates generally to incinerator systems and more particularly concerns incinerator systems wherein a burner is provided within the secondary combustion chamber for completing the combustion of the unburned products of combustion leav-' ing the incinerator chamber and wherein the products of combustion are recirculated back into the main incinerator chamber for the burning of refuse.

2. Description of the Prior Art Because of present pollution legislation and other attempts to maintain contamination of our atmosphere at a minimum, it is essential that incinerators burn materials with little or no smoke and odor. Further, incinerators utilized by private individuals and small commercial and industrial concerns must be capable of burning a wide variety of materials including wet garbage, plastics, wet and dry leaves, green grass, papers, etc. The incinerator must be simple to operate, inexpensive, and must be capable of burning the wide variety of materials completely with substantially no smoke or odor. In the prior art, a great variety of multiplechamber type incinerators are disclosed. However, in these prior art incinerators, the rate of burning is usually difficult to.control and there are no incinerators wherein the products of combustion are recycled into the incinerator chamber to cause and regulate the incineration process.

SUMMARY OF THE INVENTION The present invention pertains to an improved incinerator including a primary incinerator chamber for the burning of the refuse and a secondary combustion chamber containing a burner to complete the combustion of the unburned products of combustion which are emitted from the burning refuse in the incinerator chamber and which are transported into the secondary chamber near the burner. After the combustion of gases from the incinerator chamber have been completed by the burner and have traveled the length of the elongated secondary chamber, the gases contain ing some oxygen are free to exit through a stack to the atmosphere but some of the gases are caused to recirculate through a conduit into the primary incinerator chamber for sustaining the burning of the refuse. The rate at which the refuse burns is thus controlled by a fan which controls the rate of circulation and/or by a damper which connects the end of the combustion chamber with the incinerator chamber. The rate of burning is also self-limiting. An increased burning rate in the primary incinerator chamber produces more combustible gases which when circulated into the secondary chamber use up the excess oxygen in the secondary chamberand as this gas is recirculated into the incinerator chamber with a lower oxygen content,

the rate of burning will be reduced.

Accordingly, it is an object of the present invention to provide an improved incinerator.

It is a further object of the present invention to provide an improved incinerator which is compact, easy to operate, inexpensive and which produces substantially complete combustion with little or no smoke and odor.

It is a further object of the present invention to provide an improved incinerator wherein only one burner is required which provides an after-burning function and additionally provides the heat and oxygen necessary to burn the refuse within the main incinerator chamberi It is an object of the present invention to provide an improved incinerator wherein the rate of combustion of refuse in a main incinerator chamber is self-controlled by the recirculation of gases from the incinerator chamber through the secondary chamber back into the incinerator chamber.

It is a still further object of the present invention to provide an improved incinerator wherein the rate of combustion of the refuse within the main incinerator chamber may be varied by varying the recirculation of gases back into the incinerator chamber from the secondary chamber.

It is a further object of the present invention to provide an improved outdoor incinerator wherein the circulation is controlled by sensing means located within the incinerator system.

BRIEF DESCRIPTION OF THE DRAWINGS Referring to the drawing, there is shown a view in side elevation of the improved incinerator with the front side removed.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawing, the numeral 11 indicates a generally box-shaped housing having upper and lower walls 13 and 15, respectively, vertically extending spaced apart side walls 19 and 21, a back wall 22, and a front wall which is not shown. The housing 11 is formed of a suitable heat-resistant material and defines therein a primary incinerator chamber 23. The chamber 23 is designed to efficiently reduce solid, semi-solid or liquid wastes at specified rates, leaving the residues containing little or no combustible material. The incinerator chamber 23 is generally rectangularly shaped and has a charging door 25 located at one end thereof for the placement of refuse within the chamber. At the opposite end of the main incinerator chamber, a baffle plate 27 extends between the back wall 22 and the front wall (not shown) to define an outlet 29 for the exhaust of the products of combustion.

A conduit 31 connects the outlet 29 of the main incinerator chamber to an inlet 33 within a secondary combustion chamber 35. Secondary combustion chamber 35 is separated from incinerator chamber 23 by walls 36 and 13. Located within conduit 31 is a fan 37 and a temperature sensor 39. Fan 37 may be operated manually or controlled by sensor 39 using well-known state of the art techniques. It should be understood that the conduit means 31 function could be supplied by merely providing a wall between the chum bers with an opening into each chamber.

Secondary chamber 35 is a longitudinally extending tubular member enclosed by housing 36 formed of suitable heat-resistant material having located at one end thereof, near the inlet 33, a burner 51 which is supplied with fuel and oxygen through appropriate conduits 53. Actually, air will provide the necessary 0xygen but pure oxygen could be used. Burner 51 supplies secondary chamber 35 with an excess amount of oxygen in order to support combustion in chambers 35 and 23. Combustion chamber 35 has located within the side walls thereof a secondary combustion air source 55 and a temperature sensor 57. Temperature sensor 57 senses the temperature in chamber 35 and may control the burner 51 by well-known state of the art techniques. Burner 51 may be controlled manually as a result of the readings at sensor 57. The need for air source 55 is dependent upon the type of burner 51 used and the amount of oxygen supplied to the burner. If the burner does not supply oxygen, then source 55 is critically necessary in order to burn combustibles, whereas, the source 55 may be unnecessary if burner 51 supplies enough oxygen to support combustion in chamber 35 and chamber 23.

Located at the opposite end from the burner 51 is a stack 58 which is provided for the exhaust of the completely combusted gases. An additional source of air 59 is provided within the stack 58 which may be used to cool the products of combustion or may aid in any burning which may not yet be complete. Located opposite from the stack 58 and also near the opposite end of the secondary chamber 35 from the burner 51 is a secondary chamber outlet 61. A conduit 63 connects outlet 61 of secondary chamber 35 with an inlet 65 of main incinerator chamber 23. A butterfly damper 67 is shown pivotally attached within the conduit 61 for allowing the products of combustion from the secondary chamber to circulate through the primary incinerator chamber, or for blocking the conduit 63 and stopping the circulation of the products of combustion. Butterfly damper 67 may be another of the well-known types of dampers such as guillotines, blades or sliding blades. And, once again, conduit 61 could be merely a hole within a wall separating the chambers. As with fan 37, damper 67 may be operated manually or controlled by sensor 39 by well-known state of the art techniques.

In the present invention, the burner 51 performs its function of burning up any of the products of incomplete combustion which may be carried into the secondary chamber 35 through conduit 31 by the effluent from chamber 23 and its function of supplying excess oxygen for the incinerator chamber 23. The temperature within the secondary chamber 35 can be varied depending upon the statute in effect where the incinerators are being used and also the material which is being burned. But generally, the temperature within the secondary chamber 35 will be maintained at a minimum of 1200 F. Temperature sensor 57 is provided to maintain a minimum temperature needed to completely burn a particular type of refuse. In order to aid in the combustion of the hot gases which have exited the incinerator chamber 23, and are to be burned by the burner 51, the secondary combustion air source 55 provides an additional source of oxygen (in addition to the oxygen supplied to the burner 51, and as explained, source 55 may be unnecessary). The hot gases in the fired secondary chamber, by the time that they reach the end of the secondary chamber opposite from the burner 51, will be adjusted to contain an excess amount of oxygen and it is this oxygen which is the only means of supporting combustion in the main incinerator chamber. Either stopping the circulation of this hot gas or regulating it with a control device will control the rate of burning or incineration of the refuse at a desired combustion rate for a particular refuse.

The method of control of this hot gas circulation could be by intermittent operation of the fan 37, adjusting the speed of the fan 37, and/or by control of the damper 67. Although the damper 67 aids in the control of the hot gas circulation, the fan 37 provides the energy necessary to cause circulation. It is to be understood that other means could be used to provide and control circulation provided that they introduced energy into the system. For example, jets of oxygen or the burner 51-could be used to provide the impetus necessary for circulation. The fan 37 and/or the damper 67 could be controlled manually as a result of observing the products of combustion through the stack 58 or by making the fan 37 and/or damper 67 responsive to the temperature sensor 39 by well-known state of the art control techniques. Thus, in order to control the incineration process within the incinerator chamber 23, the fan 37 could be used to circulate gases containing oxygen more rapidly into the chamber 23 and/or the damper 67 could be used to regulate the amount of actual oxygen which is transported through the conduit 63 into the incinerator chamber 23.

In the operation of incinerator systems it is known that the quantity of oxygen which is present with the burning refuse will control the temperature at which the refuse burns and also the completeness of the refuses combustion. With complete combustion, generally the products of combustion will be carbon dioxide, water, nitrogen and ash material. The refuse in a primary incinerator chamber normally burns with an insufficient oxygen supply and incomplete combustion occurs along with decomposition of material due to the heat within the incinerator, both of which give off smoke and odors. On the other hand, if refuse should burn in the presence of too large a supply of oxygen the material may burn too fast and the rate of decomposition due to heat will be so great that it will not be possible to complete combustion of these gases in the secondary chamber 35. This would cause smoke and odors to be emitted from stack 58. This event causes'a self-limiting effect within the system since the incompletely combusted products of combustion from the incinerator chamber 23 will use up an excess amount of oxygen within the secondary chamber 35, thus providing less oxygen -to support combustion within the incinerator chamber 23 upon the recirculation of the gases. The increased burning of the refuse in the primary chamber causing smoke and odor to be emitted from the stack 58 could be used to allow less oxygen to be injected within the secondary system to control the rate of burning, or to slow down the fan 37, or to control the damper 63. Increased burning of the refuse in the primary chamber will increase the temperature of exit gases from chamber 23 so that temperature sensor 39 may be used to control the rate of burning of refuse and generation of combustible gases in chamber 23. If the temperature at sensor 39 reaches the level which is likely to generate combustible gases so fast that smoke and odors will be emitted from stack 58, then the circulation of hot gases through chamber 23 can be reduced or stopped to prevent further increases in temperature at sensor 39 and in this manner to control the emission of smoke and odor.

The temperature sensor 39 must be capable of sensing temperatures in the range of approximately 350 to 1200 F and, of course, for different materials being burned, the same temperatures may in one case be an indication of complete combustion, whereas in a second case, it may be an indication of incomplete combustion. Thus, if the completeness of the combustion is going to be adjusted or controlled by the temperature sensor 39 as opposed to viewing the products of combustion emitted from the stack 58, the general nature of the refuse being burned within the chamber 23 must be known in order to correctly adjust the control setting for temperature sensor 39 which will control circulation of hot gases and excess air through the primary incinerator chamber 23. The circulation of hot gases could be reduced or stopped by reducing the speed of fan 37, stopping fan 37, or by closing damper 67. Reducing or stopping the circulation of hot gases would reduce the temperature at sensor 39 and would reduce the generation of combustible gases in chamber 23 by reducing theinput of hot gases to the chamber 23 and by reducing or stopping combustion of refuse in the chamber 23 due to reduced oxygen or lack of oxygen to support combustion of refuse in chamber 23.

The arrangement of the incinerator chamber 23 and the combustion chamber 35 could, of course, be in any form vertical, horizontal, round or rectangular without affecting the operation of the unit. The preferred arrangement for gas flow through the incinerator chamber would be for the hot gas to enter the top of the chamber and the products of combustion from this chamber to exit near the bottom and enter the combustion chamber in such a manner as to mix with the flame for complete combustion of any smoke or products generated in the primary incinerator chamber.

Thus it is apparent that there has been provided, in accordance with the invention, a recirculating incinerator that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with a specific embodiment thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is in tended to embrace all such alternatives, modifications and variations which fall within the spirit and broad scope of the appended claims.

What is claimed is:

l. A recirculating incinerating system, comprising:

a. a primary incinerator chamber for receiving and burning refuse, said incinerator chamber having an inlet and an outlet;

b. a secondary chamber having an inlet and an outlet;

c. first means opening said outlet of said incinerator chamber into said inlet of said secondary chamber;

d. means introducing oxygen into said secondary chamber;

e. burner means located near said secondary chamber inlet for burning combustibles carried by the effluent from said incinerator chamber through said first means thus producing hot gases containing oxygen;

f. second means opening said outlet of said secondary chamber into said inlet of said incinerator chamber; g. exhaust means opening said secondary chamber to the atmosphere; and

h. means for controlling the circulation of said hot gases containing oxygen from said secondary chamber through said second means and into said incinerator chamber for controlling the rate of incineration of said refuse.

2. The system of claim 1 wherein said means for controlling the circulation of hot gases includes a fan located within said first means for controlling the rate of circulation of gases through said chambers.

3. The system of claim 1 wherein said means for controlling the circulation of hot gases includes damper means located within said second means.

4. The system of claim 1, including:

a. temperature sensing means for sensing the temperature of gases leaving said outlet of said incinerator chamber; and

b. said means for controlling the circulation of hot gases containing oxygen includes means responsive to said temperature of said temperature sensing means.

5. The system of claim 4 wherein said means for controlling the circulation of hot gases includes a fan located within said first means for controlling the rate of circulation of gases through said chambers.

6. The system of claim 4 wherein said means for controlling the circulation of hot gases includes damper means located within said second means.

7. The system of claim 1, wherein:

a. said secondary chamber is an elongated member, said inlet being located at one end thereof and said outlet being located at the other end thereof;

b. said second means is located near said second end of said secondary chamber; and

c. said exhaust means is located near said second end of said secondary chamber. 

1. A recirculating incinerating system, comprising: a. a primary incinerator chamber for receiving and burning refuse, said incinerator chamber having an inlet and an outlet; b. a secondary chamber having an inlet and an outlet; c. first means opening said outlet of said incinerator chamber into said inlet of said secondary chamber; d. means introducing oxygen into said secondary chamber; e. burner means located near said secondary chamber inlet for burning combustibles carried by the effluent from said incinerator chamber through said first means thus producing hot gases containing oxygen; f. second means opening said outlet of said secondary chamber into said inlet of said incinerator chamber; g. exhaust means opening said secondary chamber to the atmosphere; and h. means for controlling the circulation of said hot gases containing oxygen from said secondary chamber through said second means and into said incinerator chamber for controlling the rate of incineration of said refuse.
 1. A recirculating incinerating system, comprising: a. a primary incinerator chamber for receiving and burning refuse, said incinerator chamber having an inlet and an outlet; b. a secondary chamber having an inlet and an outlet; c. first means opening said outlet of said incinerator chamber into said inlet of said secondary chamber; d. means introducing oxygen into said secondary chamber; e. burner means located near said secondary chamber inlet for burning combustibles carried by the effluent from said incinerator chamber through said first means thus producing hot gases containing oxygen; f. second means opening said outlet of said secondary chamber into said inlet of said incinerator chamber; g. exhaust means opening said secondary chamber to the atmosphere; and h. means for controlling the circulation of said hot gases containing oxygen from said secondary chamber through said second means and into said incinerator chamber for controlling the rate of incineration of said refuse.
 2. The system of claim 1 wherein said means for controlling the circulation of hot gases includes a fan located within said first means for controlling the rate of circulation of gases through said chambers.
 3. The system of claim 1 wherein said means for controlling the circulation of hot gases includes damper means located within said second means.
 4. The system of claim 1, including: a. temperature sensing means for sensing the temperature of gases leaving said outlet of said incinerator chamber; and b. said means for controlling the circulation of hot gases containing oxygen includes means responsive to said temperature of said temperature sensing means.
 5. The system of claim 4 wherein said means for controlling the circulation of hot gases includes a fan located within said first means for controlling the rate of circulation of gases through said chambers.
 6. The system of claim 4 wherein said means for controlling the circulation of hot gases includes damper means located within said second means. 